In cultivation of agricultural and horticultural crops, herbicides have been used for weed control for which enormous labours have been required. However, such herbicides have often caused phytotoxicity on crops, have remained as residues in the environment and have been therefore a cause of environmental pollution. From such reasons, a development of herbicides, which can give firm herbicidal effectiveness with a lower dose and can be used without a problem of phytotoxicity, environmental residue and environmental pollution, has been required intensively.
Pyrimidyloxy-substituted salicylic acids similar to the compounds of the present invention and the sulfur homologs thereof are disclosed in Japanese Patent laid-open Nos. Sho 59-59669, Sho 62-174059, Hei 3-232884, Hei 4-77487, etc., however, there is no compound which has a satisfactory herbicidal-effect and a selectivity to crop plants.
In Japanese patent laid-open No. Hei 5-202038, it is disclosed that compounds represented by the following chemical formula; ##STR2## wherein r.sub.1 and r.sub.2 represent each independently lower alkyl or lower alkoxy; r.sub.3 represents lower alkyl or the like; x.sub.1 and x.sub.2 represent each independently O or S; a.sub.1 represents CH or N; y.sub.1, y.sub.2 and y.sub.3 represent each independently H or the like; and b.sub.1 represents CH or N, have a herbicidal effect.
It is an object of the present invention to provide herbicides which can be easily produced in an industrial scale, safe and excellent in herbicidal activity at a lower dose, and have excellent selectivity to various agricultural and horticultural crops.